The commission of inquiry looking into the loss of the UK-built Beagle 2 lander will be hoping for one piece of evidence above all else in its investigation: a picture of the stricken probe on the surface of Mars.

If it can get an image of an intact "pocket watch" robot on the Red Planet, this would significantly reduce the list of possible factors that could have blighted the mission.

"You can ask what happened to the airbags? What happened to the parachute? What happened to the computer?" said Beagle 2 lead scientist Professor Colin Pillinger.

We are going to start taking some observations of the Beagle site to try to get some documentation there

Dr Mike Malin

"But if you have a picture of what is on the surface of Mars, it would allow us to dismiss a great chunk of this and say 'forget it, look at something else'."

The Beagle team will try one last trick to get its robot to talk by sending a command to reboot the computer - but the scientists and engineers on the project admit this is a last resort and unlikely to produce a positive result.

On target

Instead, energies are now being focused on a "list of lessons learned". It means going back over the whole mission to identify weaknesses.

"This includes a reassessment of the landing site, a reanalysis of the entry using the atmospheric conditions as we know them, and going back through all the data we got on the seven-month cruise to Mars," said Dr Mark Sims, from the Beagle Lander Operations Centre in Leicester.

The mission team is convinced Beagle hit its planned landing zone - three independent groups calculated the final trajectory and produced ellipses for possible touchdown that were the same to within a few kilometres.

This should help the US Mars Global Surveyor (MGS) spacecraft as it combs the surface of the planet to get the photo everyone wants.

At the weekend the lead imager on MGS, Dr Mike Malin, presented data he had obtained on the lading site for the Nasa rover Spirit, which got down safely on 4 January.

Remarkably for images taken from an altitude of 400 km, they even reveal the depressions Spirit's landings bags left in the Martian soil as the vehicle bounced to a stop.

It's back to the bottom of the hill to start pushing that boulder back up again

Prof Colin Pillinger

"We were very surprised how bright [Spirit] was," said Dr Malin. "It has to do with the freshness of the materials on the surface - they are not covered with dust - and the particular illumination conditions under which we were viewing.

"We are going to start taking some observations of the Beagle site to try to get some documentation there. We are also using a new technique for imaging in which we are synthesising a much higher spatial resolution - 50 centimetres as opposed to our normal 150 cm."

This photographic search, which will also involve Europe's Mars Express orbiter, will go on throughout February. "If Beagle is open, it's not far off the size across of Spirit," said Professor Pillinger.

"If Spirit can be seen then Beagle can probably be seen. The parachute is 10 metres across and is a prime target. A parachute on the ground would certainly suggest we got that far."

Innovative technology

A reason for failure must be found if the Beagle team is to persuade Esa or another space authority to sanction another mission.

Jodrell built a special cryogenic receiver

Pillinger and Sims are convinced the way to go is with a dedicated flight of Beagle "pups" - probably in 2007 - that would see several robots land on the Red Planet at the same time.

But no agency would unleash these pups without first knowing Beagle's problems had been designed out of the mission.

It would be a tragedy, however, if the engineering and scientific excellence developed over the past four years were to be denied its big show.

Even in adversity, this project has pushed British researchers to remarkable levels of innovation.

Big push

Jodrell Bank, the radio telescope facility near Manchester, developed a super-cooled receiver to scour the surface of Mars for a Beagle signal at 401 MHz.

"It's probably the best that's ever been constructed in the world at this frequency," said Jodrell's Dr Ian Morrison.

"It's cooled to just 13 degrees above absolute zero, partly because the cooler it is, the less thermal noise you get and that makes it more sensitive.

"It also enabled us to use some marvellous superconducting filters built by the University of Birmingham that would allow the Beagle signal to come through undiminished but reject the vast amount of terrestrial interference that we had in that particular band."

Pillinger and Sims will be hoping MGS can deliver the all important photographic evidence and that the internal and external inquiries find the root cause of what went wrong.

The campaign then starts for 2007.

"It's back to the bottom of the hill to start pushing that boulder back up again," said Professor Pillinger.